Previous work has demonstrated the presence of a chemoreceptor system with sensory endings in the mucosa of the laryngeal area. When suitably stimulated this system may produce sustained apnea leading to asphyxial death in the piglet model. The afferent fibers are located in the superior laryngeal nerve and when electrically stimulated an identical pattern of respiratory inhibition can be demonstrated. The sensory endings are activated by the presence of water or cow milk in the laryngeal area, but are not stimulated by normal saline, glucose solutions or alterations in osmolality or pH. While a high percentage of piglets manifest sustained apnea leading to death when the laryngeal area is suitably stimulated, others demonstrate breakthrough with resumption of normal respiratory activity following a variable period of apnea. This suggest that co-factors may be operative in some animals sufficient to over-ride the inhibitory influences of the laryngeal system. The objective of these investigations is to identify and evaluate these co-factors. The first approach will be to assess changes in central respiratory drive produced by the sequential administration of chloralose anesthesia. Preliminary observations suggest that the relative potency of the laryngeal system is enhanced as central respiratory drive is reduced by this method. A second approach will be to evaluate the relationship of age and presumed developmental changes on the relative potency of this system and possible changes in sensitivity to precisely measured amounts of anesthetic agents. In addition, the contribution of the peripheral chemoreceptor system (carotid body and aortic arch chemoreceptors) will be evaluated in piglets from 2 hours to 2 months of age.